Abstract

We have inserted nonmagnetic impurity layers of Au into sputtered AlOx-based magnetic tunnel junctions (F/I/F) and Meservey–Tedrow junctions (S/I/F) in order to study their effect on the tunneling magnetoresistance (TMR) and spin polarization (TSP). Both room temperature TMR and the TSP at 250 mK decay exponentially as an interfacial Au layer is introduced between the barrier and one Co electrode, with 1/e decay lengths λTMR=11±3 Å and λTSP=14±2 Å. We also inserted a 1 Å thick Au layer at a variable distance from the barrier/Co interface and find that both the TMR and TSP recover to the undoped value with the shorter exponential length scales of λTMR=7±4 Å and λTSP=6±2 Å.